Providing a world-wide web (WWW) interface for access to TA information and special events that occur during the TA deployment.

Why does the station map take so long to load?

The station map is created dynamically, communicating with the station database
to ensure the most recent USArray station deployments are plotted. This is why there is a date-stamp
at the base of the image in the legend noting how many stations were online at that precise time.

The station map should load in under 10 seconds if you are on a T1 connection, in under 30 seconds
if you are using a 56K modem, but up to 120 seconds if you are using a 28K modem. Please be patient
and wait for the image to load – there is a lot of information being processed to create the image.

What do the column headings in the station table mean?

The station table has six columns — Station ID, Station Name, Latitude, Longitude,
Elevation and Ondate. The Station ID is a unique identifier to each respective station. The
Station Name either describes the location of the station, or is a particular location.
Latitude is in degrees (°) north, so a negative number means that the station is south
of the equator. Longitude is in degrees (°) east, so a negative number means that the
station is west of the Greenwich meridian in
London, England (the location of zero degrees longitude). Elevation is the height above sea
level in meters.

The Ondate is a number that is a combination of the year (four values) and the
Julian Day
(three values) and refers to the last time something was modified at that station (ie. a new
sensor was installed, a different sample rate was implemented, etc.). Thus, an ondate of
2004100 does not mean that the station first started operating in 2004, only that a change in
its setup occurred then: it could have been operational for 25 years prior to the reported
“ondate”.

Why are there several
solutions for the same event, often with different magnitudes
and locations?

There are several reasons for different reporting bodies
producing different locations and magnitudes for the same
earthquake. The most fundamental cause is the location and number
of seismic stations that recorded the earthquake. The magnitude and the location
of a given earthquake is preferably determined using more than one
seismic station. A suite of seismic stations distributed around the
earthquake's epicenter and have a range of source/station distances can
typically yield better location and magnitude estimates than a single
station far away. However, other factors can also introduce
additional deviations in the measurement such as differences in the
recording capabilities of the seismic sensors, the seismic analyst
making the measurement and variations in the geology and tectonics of
the region. A rule of thumb used by some seismologists is that
magnitude estimates can typically deviate by 0.5 magnitude units, and
the mapped location of the earthquake (latitude, longitude) is often
known in greater detail than the depth of the earthquake (distance from
the Earth's surface to the earthquake's hypocenter).

A second variable is by what process the event is measured, and
which scale is used. There are four different measurement scales
— surface wave magnitude (Ms), body wave magnitude (mb),
moment magnitude (Mw), and local magnitude (Ml).

What criteria do you use to name a new station/site?

A Transportable Array station code is 4 characters long.
The first three characters of a new station's station code are
based on its geographic location. The last (fourth) character
identifies the sequence of stations installed at this grid point.
Often the first planned site had complications that prevented
its inclusion, so instead of "A", you will see "B" or "C", and
so on. Normally only one station would lie in a grid point but
if a station must be relocated the scheme must easily support this
possibility. A fifth character is possible for SEED station codes,
however this character is undefined for the present time.

The geographic based naming convention is based on a grid
system with geographic placement amongst the rows and columns
defining a different part of the station code. There are rows
of stations A, B, C, etc. starting at the Canadian border and
incrementing an idealized every 75 km or so until reaching
the border with Mexico and columns starting at "01" at the
westernmost point in the US deployment plan and incrementing by
one as you move approximately every 75 km to the east. More than
26 rows are needed to accomplish this gridding so after "Z"
comes a station starting with "1". Less than 99 columns (64
in total) are needed to accomplish this gridding, so the 2nd
and 3rd characters will always be numeric. Thus the station
code takes its first character based on its latitude and the
numeric second and third characters are based on its longitude.
Due to the obvious difficulties with siting, the idealized 75km
grid spacing is adjusted to fit the conditions in the area.

Let's take as an example station A12A. The first "A" tells
us that this is a 'northern' site near the border with Canada.
The "12" tells us that it is 12 grid points in from the
westernmost point in the deployment grid. Very approximately
that is 12*75 km from the westernmost point. The final "A"
tells us this was the first location for a station at this grid
point. This ends up being a site in Montana.

Prior to final installation and certification, site codes
include a dash followed by a number that identifies the
classification of the site.

A12A-0 is an initial site for the station location A12A

A12A-1 is a potential site for the station location A12A

A12A-2 is another potential site for the station location A12A

A12A-3 is a third potential site for the station location A12A

When one of the potential sites is permitted it is referred
to by the station code A12A. The SEED station code is the station
code, the Network code for USArray Transportable Array is TA. You
may seed a station code written as TA.A12A or TA_A12A.

How can I host a USArray station?

What is SNOFLU?

SNOFLU is an acronym for Sudden Noise Onset Fixed by Lock/Unlock. It is a known sensor issue
with certain datalogger types, when for no apparent reason the station channel(s) start to get noisy.
This is fixed by a physical mass position lock and unlock process on the sensor.